The present invention relates to the technical field of the consolidation of planting substrates and/or the particle enlargement of planting substrates, more particularly for the purpose of utilizing fine-particle peat.
More particularly, the present invention relates to a method for utilizing fine-particle peat, more particularly a method for improving the firmness of planting substrates.
The present invention additionally relates to a binder composition, more particularly for consolidating planting substrates.
The present invention further relates to the use of a binder composition for consolidating planting substrates, and also to the planting substrate obtainable in this way. The present invention relates, lastly, to a planting substrate which comprises a peat comprised substrate mixture and also a binder.
Peat is an organic sediment which is formed in moors in the absence of air through incomplete decomposition of dead plant substances. Among moors, a fundamental distinction may be made between low moors and high moors, with only the peat harvested from high moors being utilized for industrial and domestic purposes.
Peat forms the basis of the majority of planting or growing substrates and potting soils which are used in horticulture both for leisure and for commercial gain. Planting or growing substrates are mixtures of selected starting materials or base materials, such as peat, wood fibers, compost or else coir pith, for example. These mixtures are admixed with fertilizer and also, optionally, optimized with adjuvants. In this way it is possible to provide substrates or potting soils adapted to the specific requirements of the particular plants. The substrate mixtures or potting soils serve as root space for the horticultural plantings.
Various grades of peat are used for growing substrates, the composition of these grades being tailored to the specific requirements of the growing of different types of plant. As well as different kinds of peat, such as white peat and black peat, adjuvants such as coconut or wood fibers, fertilizers, minerals, and also clay, sand, lime or perlite are used for producing the substrates or potting soils.
There are various ways in which the various peat substrates can be mixed with the plant-specific adjuvants. Use of conveyor belt systems and drum mixing machines is commonplace for producing homogeneous mixtures.
White and black peats and also various sub-varieties of peat differ in their degree of decomposition and hence in the proportion of plant structure that is still perceptible. A further subdivision of the substrate mixtures comprising peats or peat constituents is made according to their density, which may be in the range from about 100 kg/m3 to about 800 kg/m3, and also according to the consistency and particle size. Grades which can be differentiated are very fine, fine, medium, coarse, and extra-coarse, possibly with further classification, such as fibrous, for example. Black peats, for example, are generally classified as fine or very fine. For white peats, conversely, particle sizes up to 10 mm are classed as fine or very fine, up to 25 mm as medium, and larger than 25 mm as coarse.
While peat is an outstanding basis for growing substrates of any kind, up to 40% of the cut peat cannot be used for producing growing substrates, especially for commercial horticulture, on account of its consistency, more particularly on account of a pronounced fine-particle nature of the peat. Relatively large aggregates and agglomerates of the peat fall apart on mechanical processing, and/or cannot be processed to homogeneous growing substrates with the other starting materials and/or adjuvants.
In commercial horticulture, plants are generally grown according to the following principle: the substrate mixture for plant growing is introduced alternatively into plant trays or planting pots or is pressed into shape in the form of what are called soil blocks. The plant trays used—often referred to for short as trays—can accommodate around 40 to 250 substrate plugs, as they are known, depending on construction. Substrate plugs are shaped bodies of growing substrate or planting substrate, which are filled into the plant trays or formed by filling of the substrate mixture into plant trays. Filling of trays is accomplished customarily by hand or using tray fillers, allowing different throughputs according to construction.
After a germination and growth period determined by the nature of the plant, the plant together with its root system and surrounding substrate plug is transferred to a planting vessel of the next size up. Apparent here are substantial differences between individual peats or substrates. Certain substrates afford high firmness, meaning that the shape of the plugs is retained when the plants are being transplanted. With other mixtures, this is not the case. During transplantation, the substrate parts from the root system—in other words, only the plant can be transplanted, a feature generally unwanted by the commercial end user.
Since not all solid or dimensionally stable peat mixtures are of equal usefulness as substrates for all plants, technical remedies are required in the case of loose peat mixtures. One remedy is provided by what are called paper plug machines. These machines surround a defined amount of planting substrate with a paper or nonwoven material in order to maintain the plug in shape mechanically. After they have been surrounded, the paper plugs are inserted into the trays manually or by means of robots. Disadvantages associated with this method are the performance of an intermediate step, the capital investments in the form of machinery and paper material required, and also additional time taken.
In commercial horticulture, therefore, it is desirable to obtain any peat or substrate mixture in a form which makes the use of growing aids such as paper plugs unnecessary and allows pot, tray or soil-block application.
In the prior art, therefore, there has been no lack of attempts to consolidate growing substrates based on peat. Thus EP 0 971 015 A1 describes the use of a water-isocyanate prepolymer emulsion for consolidating planting substrates. The emulsion is prepared by mixing an isocyanate prepolymer with water and must thereafter be further-processed within a few minutes, by mixing with the planting substrate, in order to produce the desired shaped bodies.
Moreover, US 2006/0248795 A1 describes a method for producing a consolidated growing substrate wherein a substrate mixture is admixed with a thermoplastic, biodegradable binder, the binder being subsequently melted by supply of heat. As a result it is possible to produce shaped bodies based on a growing substrate. The use of biodegradable hotmelt adhesives is complicated and costly in terms of apparatus and energy, however, making the method neither economically nor environmentally rational to implement.
EP 1 330 949 A1 describes a method and apparatus for producing shaped bodies consisting of planting substrate and of consolidating agent combined with said substrate. In this case, isocyanate prepolymers are mixed with water to form an emulsion which is then added to a planting substrate. The mixture is subsequently introduced into matrices and compacted, giving shaped bodies.
WO 00/60922A1 as well, lastly, describes a method for producing shaped bodies based on isocyanate prepolymers and planting substrates.
While the aforementioned methods do make it possible to consolidate planting or growing substrates, the sole products are shaped bodies—in other words, it is not possible to custom-tailor the particle size of the peat. For many systems, moreover, there is no biodegradability, which limits the usefulness of the methods.
In the case of the prior-art methods, furthermore, it has proven disadvantageous that oftentimes they must be carried out at elevated temperatures or feature only extremely short working times before the setting of the binder.
It is an object of the present invention, therefore, to provide consolidated planting substrates and also planting or growing substrates with which the problems and disadvantages outlined above, occurring in connection with the prior art, are at least largely avoided or else are at least diminished.